Laser radar (LADAR) systems are useful as sensors for autonomous targeting guided weapons. LADAR systems function by scanning one or more laser beams over a target range and receiving beams reflected from objects situated within the target range. The reflected laser beams provide, via range finding apparatus, reflectance data including the distance to an object and the intensity of the reflected beams so that a profile of the target range can be constructed. False-color or gray-scale range and reflectance intensity images of the target range can be displayed based on the target range profile.
A non-real-time single channel diode laser radar and a real-time 24 channel scanning diode laser array implementation of an imaging LADAR system is described in Gustavson et al., "Diode-laser radar for low-cost weapon guidance", SPIE Vol. 1633 Laser radar VII (1992), pp. 21-32. A more powerful diode pumped Q-switched laser employed in an imaging LADAR system is described in Andressen C. C., "A 1.32 micron, long range, solid state, imaging LADAR", SPIE Vol. 1694 (1992), pp. 121-130. The disclosures of the preceding articles are hereby incorporated by reference herein.
A number of problems arise with existing LADAR systems. Typically, LADAR systems scan a large area for targets and collect a large amount of reflectance data which must be processed in order to determine potential targets. The response time necessary to locate, recognize, and classify targets is an important factor in targeting. Both sides in a conflict may employ LADAR systems for target detection so response time can become a critical factor.
There are two main limitations on response time. First, a scanning range finder typically scans a single laser over the range finder's entire field of view to collect reflectance data. The time required to finely scan a laser beam over a range finder's entire field of view, which is typically a large area, can be significant. The traditional solution to this problem is to employ a plurality of lasers having offset fields of view that collectively span the range finder's entire field of view. In this manner, reflectance data for a large field of view is quickly collected. However, the cost and complexity of such LADAR systems is high.
Second, response time is bounded from below by the time required for target recognition software to verify a target. Additionally, there is the general problem of target recognition and classification, which is particularly acute in high-clutter environments. For example, since it is necessary to discriminate background objects such as large rocks, a target recognition process must have very good discrimination characteristics.
A target classification process described in Gustavson et al., a reference cited above, utilizes a recognizer module which scans through an elevation image and identifies and labels all objects in the elevation image based on a comparison with pre-stored target signatures. A further pass through the elevation image then attempts to label sub-regions within each object. From this, a labeled image mask is produced which is fed to a classifier module. The classifier module extracts one object at a time for target classification, and discriminatory rules are applied until a target is verified. An aim point is then computed.
A target classification process described in Andressen, cited above, utilizes pre-stored critical points on target signatures at a number of aspect angles for comparison purposes. Points on the image derived from the LADAR are scored as to the likelihood that they belong to one of the pre-stored critical points.
Conventional laser scanning systems are described in Laser beam scanning, Gerald F. Marshall (Ed.), Marcel Dekker, Inc., 1985.
A document entitled "SIcam.TM.--A PC compatible digital instrumentation camera incorporating a large pixel 512.times.512 format charge injection device (CID)", by CID Technologies Inc. (CIDTEC), Liverpool, N.Y., describes a microprocessor-based camera which skims accumulated pixel charge and/or non-destructively reads pixel information, enabling the system user to monitor events and dynamically adapt application exposure in real-time for the entire array of individual pixels.
The disclosures of all of the above publications are hereby incorporated by reference.